1. Field of the Invention
This invention relates to interface circuitry and, more particularly, to a multi-mode time division multiplexing interface circuit.
2. History of the Prior Art
Digital Signal Processors (DSPs) have been developed to support analog telephony applications. Typically these DSPs include one or more serial data interface ports with the capability to support one or more analog Coder-Decoder (CODEC) chips such as an Analog Interface Chip (AIC), a Voice-based Audio Processor (VAP), or a Logarithmic Pulse Code Modulation (PCM) CODEC Chip. These CODEC chips provide a single channel analog interface and therefore the design of the DSP serial data ports is oriented toward supporting a single channel.
As telephony techniques and technology have become increasingly sophisticated, a need has arisen to apply DSPs to telephony applications in a multi-channel environment. A typical multi-channel environment uses time division multiplexed (TDM) channels, with different users each being assigned a time slot or set of slots of a single channel on which user data is transmitted and received.
In order to use a DSP having data interfaces designed for single channel analog applications in a multi-channel TDM environment, it is necessary to design fixed hardware buffer structures for each different TDM application. If the fixed hardware buffer structure specific to a certain TDM application is designed into a DSP, the DSP does not allow the flexibility of using the DSP in a single channel analog environment. An added disadvantage is that once fixed hardware is designed for a specific TDM application, it cannot be easily modified for use in other TDM applications.
It would provide an advantage then to have a DSP interface circuitry that is configurable and programmable to support use of a DSP in differing telephony applications. It would be particularly advantageous if the interface circuitry is capable of supporting various multi-channel TDM applications and, also was capable of supporting single channel interfaces of analog telephony devices.